This collaboration has as its goal the development of therapies for three different poxvirus diseases, including smallpox, perhaps the most dreaded agent in bioterrorism. The consortium includes two university laboratories (MIT and Arizona State University), specializing in protein-DNA interactions and in pox virology, plus a not-for-profit institute, Southern Research Institute, skilled in drug discovery and development. The proposed therapy is based on the E3L molecule, which is a virulence factor that acts by binding to left- handed Z-DNA and is encoded in most pox genomes. Vaccinia virus, when injected into a mouse, is lethal in slightly more than a week. The 25 kD E3L protein contains two domains. The N-terminal domain binds left-handed Z-DNA. In experiments informed by structural studies, it has been shown that mutations weakening Z-DNA binding result in lower pathogenicity, while loss of Z-DNA binding leads to a complete loss of pathogenicity. Variola, the agent of smallpox, has an E3L molecule virtually identical to that in Vaccinia. We propose to develop a therapy for Vaccinia and Variola infections by discovering a small molecule that binds to the Z-DNA binding domain of E3L, such that E3L can no longer bind to Z-DNA, thereby interfering with the pathogenicity of the virus. The Monkeypox virus has a modified E3L that is likely to bind Z-DNA. Drug design will be aided by solving the structure of co-crystallized candidate drugs with E3L. The discovery of molecules blocking E3L binding requires high throughput screening, chemical modification of lead compounds and appropriate animal tests to confirm in vivo activity. Testing of potential Variola therapies will involve the Center for Disease Control. RELEVANCE (See instructions): This proposal deals with developing therapeutic drugs for treating viral diseases such as Vaccinia (used for vaccination), Variola (the agent of smallpox) and Monkeypox (recognized as lethal for man). Due to concerns about bioterrorism, it is important to have such drugs available in case of an attack.